Conventional bacteria analyzers are known for analyzing bacteria contained in samples such as blood, urine and the like using flow cytometry (for example, refer to EP1136563, U.S. Laid-Open Patent No. 2004-219627).
The bacteria detection method disclosed in EP1136563 creates a two-dimensional distribution diagram based on a combination of the forward scattered light intensity and the forward scattered light pulse width. Groups including bacteria are identified using the two-dimensional distribution diagram, and a new two-dimensional diagram is created based on the combination of the forward scattered light intensity and the fluorescent light intensity only for the identified groups. In this way bacteria can be separated from other components (crystals, broken cells and other impurities) according to the differences in fluorescent light intensity, and the number of bacteria can be more precisely counted.
The bacteria measuring method disclosed in U.S. Laid-Open Patent No: 2004-219627 differentiates bacilli and cocci based on differences of slope in the bacteria distribution states. In order to distinguish between bacteria and other components (crystals, broken cells and other impurities), a scattergram is prepared beforehand by plotting the forward scattered light intensity and fluorescent light intensity on the two axes and presetting the range in which bacteria appear in the scattergram, then counting the number of particles appearing within the set range as the number of bacteria.
The ranges in which bacteria appear in the scattergram differ greatly depending on the type of bacteria and state of proliferation. There are therefore normally circumstances under which a large number of bacteria may appear in a region in which impurities appear depending on the type of bacteria and state of proliferation. In the disclosures of EP1136563 and U.S Laid-Open Patent No. 2004-219627, however, a large number of bacteria may appear in region with impurities when a fixed region is set as the bacteria count region regardless of the type of bacteria and state of proliferation, such that there is need for improved precision in the bacteria count because in such instances bacteria in the impurity region may be excluded from the count object.